The invention relates to displaying images formed on an image bearing layer of a lenticular image, and in particular display systems which provide illumination to lenticular images. Specifically, this invention describes a novel backlit display system which provides selective viewing of individual images formed onto an image bearing layer of the lenticular image.
The term lenticular image, as used herein, is meant to describe the class of images that are formed on the back side of a lenticular support or substrate and which provide the ability to selectively view at a certain viewing angle a single image from a set of images. The lenticular substrate is a parallel array of cylindrical lenses (or lenticules) made of a suitable clear material which forms the substrate onto which specially formatted image data is applied. This specially formatted image data as described in the art, consists of separate parallel image lines or image views placed behind and along the length of each lenticule. These image view lines are alternatively called lineform or integral image data. Using the high resolution imaging technology available today, there are usually many distinct image view lines arranged in parallel behind each lenticule. As the number of view lines behind each lenticule increases, the spacing between each line must decrease proportionally for a given lenticule size. It is not unusual to have image view line spacing on the order of 12 to 15 microns or less depending on the imaging technology used to generate the images.
The thickness of the lenticular substrate is designed so that when the image data is applied to the back surface of the substrate, the image view lines will be located at the back focal distance of each of the individual lenticules. This allows each image view behind a given lenticule to be seen through the lenticule separately from the other image views as the lenticule is observed at different view angles. This is because the cone of light that emanates off a view line, either from transmittance or reflection, to the lenticule lens surface refracts and forms a mostly parallel ray of light exiting the lenslet at an angle determined by the placement of the view line relative to the lenticule. The width of the parallel rays emerging from the lenticule will have the same width as that of the lenticule and thus the view line""s width will be seen magnified to that of the lenticule.
The resolution of a lenticular image, in the direction perpendicular to the lenticules, will always be equal to the pitch of the lenticular array. The actual number of different images that can be seen as the viewing angle changes will be the number of image lines placed behind each lenticule. Of course there will always be a practical limit on exactly how many distinct views can actually be resolved. This limit will be determined by such things as the optical quality of the lenses of the lenticular substrate, the resolution of the media used to form the image lines and the manufacturing tolerance for the thickness of lenticular substrate.
Depending on the content of the original source images and how these source images are formatted and applied to the lenticular array substrate, different lenticular image effects can be produced. If the original image source data contains multiple parallax images of a scene, the data can be formatted onto the lenticular substrate in such a way as to produce an autostereoscopic image. In this instance the lenticules are oriented vertically as a person views the stereo image. Since each eye views the lenticules from different angles, each eye sees different views behind the lenticules and the image appears to have the quality of depth.
Another common use for lenticular imaging is to view motion or dynamic image content. In this case a temporal image sequence, which might be from a video clip, is sampled, formatted and applied to the lenticular substrate. When used in this application the lenticules are oriented horizontally and in this case each eye will see exactly the same view. The lenticular image can then be rotated by hand along the horizontal axis of the image so that the eyes see sequences of image views producing the effect of motion or scene change. A slight variation on this method is to place several different image scenes in sequence together on one lenticular card forming a collage. The images may be thematically related but the individual images themselves are usually different pictures. Thus the images may be scenes relating to a family vacation or perhaps a wedding. The number of individual pictures displayed on this type lenticular card is usually limited to two to four. This is due to the fact that as more pictures are added to the lenticular card each individual picture will be seen over a smaller total viewing angle. This makes it difficult for the person viewing the card to see only one image at a time.
As explained above selective viewing of individual images is accomplished by the cylindrical lenses and the fact that they restrict the view each eyes sees. The changing of views that are visible to each eye is accomplished by changing the viewing angle of the eyes relative to the centerline of the lenticules. This means that either the lenticular media must be rotated or the location of the viewers eye must be physically moved to see the different image views of the lenticular image. Therefore, in actual use, small lenticular cards are usually held in the hand and rotated, while large lenticular images are usually backlit and firmly mounted with the lenticules in the vertical direction, requiring the viewer to walk past the lenticular image.
There are, however, several shortcomings to the above described methods of viewing lenticular images. In the first example, wherein the lenticular image is held in the individual""s hand and rotated, it is usually only practical for one person to see the image at one time. This is in contrast to normal photographs which can be viewed by more than one person because there is only one view and everyone can see the same image. With a lenticular image this will not be true and so a second person looking at the lenticular image will usually not see the same image as the person holding the card.
Another problem, especially with lenticular collage images, relates to proper illumination of the lenticular image. Unfortunately, the lenticular effect that allows only one view to be seen at a specific angle also has the same effect with illumination. A directed light source can not illuminate all the views because the lenticules will direct the light to only those views that are at the viewing angle of the light source. If the light source under which the lenticular image is being viewed is at a angle different than the angle of the viewers eyes to the lenticular card the image will appear very dark. The only remedy is to move the viewing orientation of the card until the light source illuminates the same views as those that are being looked at. Usually this will occur when the light source is behind the person viewing the lenticular image.
In the second example above, large lenticular images mounted in some type of frame and perhaps backlit require the observer to physically change their position to see the different views. In this type of display the lenticules are typically oriented in the vertical direction so as the observer walks past the display, different views will be seen. Problems with this type of viewing are that at the point where one view switches to the next, the left and right eye see different views and the image is confusing. Also, it is inconvenient for the person who wants to see a previous view because they are forced to walk back and forth to the correct viewing angle.
U.S. Pat. No. 6,078,424 describes a type of image display device that utilizes lenticular screens. The basic purpose of this display is to allow viewing of what is termed xe2x80x98image bearing membersxe2x80x99 that contain the image information. Essentially, the image bearing members are what are typically bonded to the lenticular substrates, or screens in the ""424 patent, that allow for correct viewing of lenticular images. However, this image display device has a its own lenticular screen through which the image bearing members that have been formatted for viewing through a lenticular screen are viewed. In one embodiment the lenticular screen is supported on flexures that allow the screen to be accurately translated in a direction parallel to the plane of the screen and perpendicular to the long axis of the lenticules. The difference with this display is that once an image bearing member has been placed into the display, that is behind the lenticular screen, the screen is translated across the image bearing member and thus each successive view can be seen. This is in contrast to a typical lenticular image which would be rotated about the long axis of the lenticular screen. A means is also described to provide for the backlighting of the images to improve viewing in poorly lit environments. The display allows for different image bearing members to be readily changed for the viewing of different images on different image bearing members.
There are difficulties however in the practical realization of this type of lenticular display device due to the extremely precise registration that is required to be held between the lenticular screen and the lenticular images. This precise registration is not only in spacing and flatness between the screen and the images but also in parallelism of lenticules and image lines. The spacing between the lenticular screen and the image bearing member would have to be held to less than 0.0254 mm across the surface of the card. This would require a lenticular screen that could maintain this flatness over its life while being subjected to everyday normal use. In addition, the image bearing members would also have this requirement at least in how flat it would have to be held in the viewer. This type of flatness is difficult if not impossible using plastics for the materials. Another very difficult technical issue is in matching the pitch of the lenticular screen with the images on the image bearing member. The pitch of the lenticular screen of the viewer would have to be held to a tolerance better than 0.1%. The image bearing members produced for this type of display likewise have to maintain this tolerance over temperature and humidity variations.
It is therefore desirable to have a display device capable of sequentially displaying lenticular images automatically that would provide sufficient illumination for the images independent of ambient light conditions. It would also be beneficial to have a display that could be used to display lenticular images which were observable by multiple viewers at the same time from different viewing positions. In addition, it would be desirable to have a display that could selectively display the individual image views of a lenticular image and transition from one image to the next at different rates and in any desired order. Finally, it would be valuable for such a display device that has the capability of displaying lenticular images which are not be limited to a single set of images. Therefore, a display device that has the ability to quickly and easily change from one set of lenticular images to a different set would be extremely useful.
It is one object of this invention to provide a method and apparatus for backlighting lenticular images in a way that selectively illuminates only one of the image views of the lenticular image at a time. It is a further object of this invention to provide a method and apparatus that can change from illuminating any one of the image views of the lenticular image to illuminating a different image view enabling the time sequential viewing of each of the lenticular images without the necessity of moving the lenticular media or the position of the viewers eyes. It is a third object of this invention to provide an apparatus that can be quickly configured to display different sets of lenticular images.
The present invention is directed towards providing a novel display apparatus for sequentially displaying each of the different image views of a lenticular image where each image view can be automatically illuminated in turn.
According to one aspect of the present invention a method of selectively illuminating one image from a set of images formed on an image bearing layer of a lenticular image comprises the steps of providing a source of illumination which is projected through a lenticule side of the lenticular image. The light passing through the lenticules emanate from a point located at a viewing distance of the lenticular image. Locating the illumination source such that an angle formed by a ray from the illumination source relative to a line at a center of the lenticular image and normal to an image plane corresponds to a correct viewing angle of a first image from the set of images. The illumination is a line source which is parallel to a longitudinal axis of the lenticules.
The display apparatus consists of an illumination source whose light is directed to the lenslet side of the lenticular media. The lenticular image must be of the transmission type wherein the illumination source passes through the image. The illumination source divergence angle is directed such that it conforms to the positional location of the individual image views behind each lenticule. In this way only certain selected image views are illuminated at one time and therefore become visible when viewed from the side opposite of the lenticular substrate. This is the same mechanism that allows the eye to see only certain image views at any one location. By then changing the angle of the illumination source with respect to the lenticules a different image view can be selectively illuminated. A suitable diffuser material is placed on the image side of the lenticular image to diffuse the light coming from the selected view to give it a wider viewing angle.
The invention provides a novel display device for the automatic viewing of lenticular images that does not require either the lenticular image or the viewer to move in relation to each other. Also multiple viewers will see the same image even though their positions relative to the lenticular media may be different.
These and other aspects, objects, features, and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiments and appended claims, and by reference to the accompanying drawings.